i can confirm this bug,
replicated in: forge-1.15.2-31.1.0 (recommended) and forge-1.15.2-31.1.47 (latest as of today) [no other mods installed]
this bug does NOT occur in vanilla minecraft 1.15.2
bug description:
when items are pulled from doublechests with a hopper/hopperminecart, comparators going 'out' of this double chest do not update properly, until the doublechest is opened (and thus itself block-updated) by the player manually.
i noticed that basically only the 3 comparators going out of the corresponding half (*) of the doublechest from which the last item was pulled update correctly and the 3 comparators on the other side no not update. it does not matter from which side of the doublechest the items got pulled by a hopper, only in which half the last item was located inside the chest.
(* standing in front of a doublechest, the 'left halft'/'left block' of the inventory corresponts to the top 3 inventory rows of this chest, and the 'right half' of the chest to the bottom 3 inventory rows)
